Whatever may be the truth as to the Mendota conference, it is unjust to Douglas to say that he was surprised by the question, or that his answer was a mere extemporized feat of ingenuity to meet an embarrassing exigency. Long before this and on many occasions he had announced his opinion that the people of a Territory could by unfriendly legislation, in defiance of the Constitution, the Supreme Court and Congress, effectually prevent slavery among themselves. It was one of his most deliberately formed, openly avowed and widely known opinions. It is incredible that Lincoln and his advisors were in doubt how he would answer the question. Whatever may be our view of the soundness of his doctrine, it is not just to the ablest debater and foremost statesman of the time to say that he was taken by surprise and driven into a corner by a question which, as he was taken by surprise and driven into a corner by a question which, as he said then, he had answered a hundred times from every stump in Illinois. The third debate was held at Jonesboro, near the southern boundary of the State, on September 15th. Douglas, in his opening speech, stated anew his now familiar argument that the Republican party was sectional, threatening to disrupt the Union by its slavery agitation, while the Democratic party was national, with a wholesome creed, alike applicable in all latitudes. Lincoln and Trumbull had conspired to abolitinize the old parties and secure seats in the Senate. Lincoln's doctrine of the house divided against itself was examined and the implied threat emphasized that Southern institutions must be overthrown and a dead level of uniformity reached in order that the Government should stand. The finality of the Dred Scott decision and the exclusion of negroes from the Declaration of Independence were insisted on. Much of the speech was devoted to the local and transient questions of Illinois politics. Lincoln, replying to the charge that the slavery agitation was the result of the aggressive attitude of Northern Abolitionists, again insisted that the propagandists of slavery were the aggressors, having attempted to change it from a local and declining institution and spread it through all the Territories, removing it "from the basis on which the fathers left it to the basis of its perpetuation and nationalization." The agitation began with the repeal of the Missouri Compromise. "Who," he asked, "did that? Why, when we had peace under the Missouri Compromise, could you not have left it alone?"